Combination adsorption and dewaxing process



Dec. 11, 1956 J. VAN D. FEAR ET AL Filed Oct. 22, 1954 2 Sheets-Sheet l 4 rx --16 Stock Q!) 8 l3 I? l2 u Adsorption 3O Zone 46 25 l l9\ 24 2| 2() 23 I Raffipote t t I Flflcilon Fraction 27 3I Aromatic 7 Product 1! 32 46 Dewaxing Zone Fig.

Refined Oil 39 L Wax INVENTORS. JAMES VAN DYOK FEAR ARTHUR D. MOSCRIP W O, ATTORN Y 1956 J. VAN D. FEAR ETAL. 2,773,803

comsmnon ABSORPTION AND DEWAXING PROCESS Filed on. 22,-1954 2 Sheets-Sheet 2 Dichloride Pentane I Benzene INVENTORS.

JAMES DYCK AR 3 ARTHU MOSC ATTORN Y United States Patent '0 COMBINATION ABSORPTION AND DEWAXING PROCESS James Van Dyck Fear, Media, and Arthur D. Moscrip, Swarthmore, Pan, assignors to Sun Oil Company, Phiiadelphia, Pa., a corporation of New Jersey Application October 22, 1954, Serial No. 464,064

12 Claims. (Cl. 196-18) This invention relates to a process for preparing lubricating oil having low pour point and improved viscosity index from a waxy lubricating oil stock. More particularly, the invention is directed to a combination process involving an adsorption step for selectively removing aromatic components from the charge stock and a dewaxing step for separating the waxy constituents.

The. upgrading of lubricating oil stocks with respect to both viscosity index and pour point characteristics generally has been done heretofore by steps which are separate and independent of each other. Solvent extraction is most usually employed to prepare products of high viscosity index, utilizing various solvents such as furfural, sulfur dioxide, phenol, propane-cresylic acid, etc. Reduction in the pour point of oils is commonly efiected by solvent dewaxing at low temperatures, employing a suitable solvent such as propane, methylethylketone benzene, various chlorinated hydrocarbons and the like. These two types of operations have been used in sequence, either by solvent extraction first and then dewaxing or by dewaxing followed by solvent extraction; but the practice of each operation normally has been conducted independently of the other.

The present invention provides a combination process involving the steps of removing aromatic components from the charge stock and thereafter dewaxing the saturate-rich fraction, wherein the steps are integrated with each other so that certain solvent materials are utilized in common in the two steps. This afiects various economies as compared with the prior practice of utilizing independent operations.

In one embodiment of the invention, the waxy charge oil is diluted with a relatively low boiling saturated hydrocarbon diluent, for example, pentane, and the mixture is treated with silica gel to selectively adsorb the aromatic components. The silica gel is then treated with a desorbing agent composed mainly of ethylene dichloride to displace the charge hydrocarbons from the gel. The eflluent from the silica gel is collected as two fractions one of which may be designated as an extract fraction and theother a rafiinate fraction. The extract fraction is composed mainly of the aromatic charge components in admixture with ethylene dichloride and a relatively small amount of pentane. By suitable distillation ethylene dichloride and a minor amount of pentane are recovered from the extract fraction, either together or separately for re-use in the process.

Referring further to the foregoing embodiment of the invention, the rafiinate fraction contains the saturate components of the charge stock including wax, in admixturev with ethylene dichloride and vpentane. The solvent portion of this fraction is regulated, prior to the dewaxing step, so that the ratio of total solvent (i. e. ethylene dichloride. plus pentane) to charge stock components therein is within the range by volume of 1:1 to 6:1 and suchv that the-ratio of ethylene dichloride to pentane is. within the range by volume; of 70:30 to. 98:2,

more, preferably within the range.- ofv 88,: 1210 95:5. This.

Patented Dec. 11, 1956 regulation of composition entails the removal by distillation of a part of the pentane present in the raflinate fraction as obtained from the silica gel treatment, and the recycling to the resulting rafiinate material of a part of the ethylene dichloride-pentane mixture recovered from the products of the dewaxing. step. The pentane which is distilled from the raflinate fraction is re-used as charge diluent, while the excess ethylene dichloride-pentane mixture obtained after the dewaxing step is returned for use as desorbing agent in admixture with the ethylene dichloride recovered from the extract fraction.

A second embodiment of the invention is generally similar to the one described. above, but it involves the use of a mixture of ethylene dichloride and an aromatic hydrocarbon of the Cs-Cs range. (e. g. benzene) as the desorbing agent, and the distillation of substantially all of the saturate hydrocarbon diluent (e. g. pentane) from the raiiinate fraction prior to the dewaxing step. In this embodiment the ethylene dichloride and benzene in the feed to the dewaxing step are maintained in a volume ratio Within the range of 40:60 to 98:2, more preferably within the range of 70:30 to :10. The total amount of solvent to charge stock components in the feed to the dewaxing step again is maintained in the range of 1:1 to 6:1.

The invention can also be practiced by operating with conditions intermediate of those for the two embodiments described above. In such procedure, the desorbing agent is composed of ethylene dichloride, an aromatic hydrocarbon (e. g. benzene) and a saturate hydrocarbon (e. g. pentane),,with the ethylene dichloride content being within the range of 40-98% by volume depending upon the proportion of benzene to pentane in the mixture. The ratiinate fraction from the adsorption step is distilled to remove only part of the pentane therefrom, so that the material sent to the dewaxing step still contains pentane in admixture with ethylene dichloride, benzene and the saturate-rich charge components. The proportions of the three solvent constituents of this mixture should be within certain limits as hereinafter more fully specified by means of Fig. 2.

The invention is described more specifically hereinafter with reference to the accompanying drawings in which:

Fig. 1 is a schematic illustratoin of a manner of practicing the process according to the invention; and

Fig. 2 is a three-component diagram setting forth composition limits of the solvent portion of the rafiinate material introduced to the dewaxing stepof the process.

Referring to Fig. l, the charge stock which can be any distillate hydrocarbon fraction boiling above 550 F. and containing wax and aromatic constituents, enters the system through line-10 for treatment in adsorption zone 11. The charge stock is first admixed with a relatively low boiling saturate hydrocarbon distillate which is obtained from tank 12 and sent through line 13 to line 10. For purpose of illustration this diluent will be referred to as'pentane, although any other saturate hydrocarbon of the C3-C6 range or mixture of such saturates can be used as the diluent. The amount of diluent added may vary depending upon the viscosity of the charge stock but usually will'b'e in the range of 30 300 7 based on the volume of the charge oil.

The liquid mixture of oil and diluent is periodically introduced through valve-14 and line 15 into the adsorber 11 which contains a packed bed of silica gel.

and liquid desorbing agent is added from tank 17 by adsorb the aromatics and then: elfect displacement of charge hydrocarbons through the silicagel bed into outlet Aftereach such addition valve 14 is closed, valve 16 is opened" line 19. Theamounts of chargeoil and desorbing agent introduced to adsorber 11 during each cycle may vary considerably depending largely upon the nature and composition of the. charge; 'but typically the amounts of charge oil and desorbing agent added per cycle are, respectively, within the ranges of 0.03-0.15 and 0.08-0.16 gal. per lb. of silica gel. The adsorption-desorption operation in adsorber'll conveniently may be conducted at ordinary ambient temperatures, for example; 60-120" F., althoughhigher temperatures can be used if desired, for example, temperatures up'to 200 F. If elevated temperatures are employed, the viscosity of the charge oil is correspondingly lowered so that the amount of diluent added from tank 12 may be reduced accordingly;

While only one adsorber 11 is shown in Fig. 1, it will be understood that two or more separate adsorbers may be used with. their operating phases being staggered so as to permit the charge stock to be fed to the system continuously.

I In each cycle of the adsorption-desorption operation the efiiuent stream issuing from adsorber 11 is segregated into two fractions as follows: 1) a rafiinate fraction which contains the saturate-rich portion of the charge oil including wax in admixture with desorbing agent and pentane; and (2) an extract fraction which contains the aromatic-rich portion of the charge oil in admixture mainly with desorbing agent and generally containing a small amount of pentane. As indicated in Fig. 1, the rat-finale fraction is removed through valve and line 21 to. distillation tower 22 while the extract fraction is alternately withdrawn through valve 23 and line 24 to distillation tower 25. In practice surge tanks (not shown) would be included in lines 21 and 24 so that the materials could be fed therefrom continuously to towers 22 and 25, respectively.

7 In the distillation step in tower 25, all of the desorbing agent and any pentane diluent that is present in the extract fraction is removed overhead and returned through line 26 to tank 17 for re-use. If desired, an-

other distillation tower (not shown) may be provided hence it isv usually uneconomical to provide such other distillation tower. Aromatic-rich oil is obtained from the bottom of tower and is removed from the system I through line 27.

The distillation for the ratfinate fraction in tower 22 is conducted so as to remove pentane diluent which is then returned via line 30 to tank 12. All or only a portion of the pentane is so removed, depending upon which of the previously mentioned embodiments of the invention are being practiced. This distillation step serves also as a means of regulating composition of the solvent contained in the resulting rafinate material, as required for successful operation of the subsequent dewaxing step. Such rafi'inate material is then transferred from tower 22 through line 31 to the dewaxing operation.

As previously indicated, it is within the scope of the invention to practice the process with various combinations of the solvent components in the dewaxing step.

All such combinations include ethylene dichloride in amount between 40% and 98% of the total solvent in the dewaxing feed. The composition of solvent for these combinations is specifically defined by Fig. 2 which is a composition diagram for the three components ethylene dichloride, benzene and pentane. For successful practice of the dewaxing step, the solvent composition must bewithin the area ABCD. If the proportions are such that the'compositionfalls outside of this area ABCD, satisfactory operation'cannot be achieved due either'to low yield of dewaxed oil of the desired pour point or' to an inordinately low dewaxing temperature being required to secure the desired pour point. Hence the feed to the dewaxing step must be regulated such that its solvent composition is maintained within the area ABCD of Fig. 2. Best results are obtained when the solvent composition is within the area EFGI-L' Examples of preferred solvent compositions as determined by Fig. 2 are as follows:

Percent Percent Percent Ethylene Benzene Pentane dichloride Examples of other solvent compositions withinthe scope of the invention but WhlCh are not preferred are:

Percent Percent Percent Ethylene Benzene Pentane dichloride Fig. 2 has been described above with specific reference topentane and benzene as the other solvent components in the system; Other saturate and aromatic hydrocarbons are equivalent, however, to pentane and benzene respectively. As previously stated any Cs'-Cs saturate hydrocarbon or mixtures thereof can be used in the process in place of pentane. Likewise, any aromatic hydrocarbon of the C6-C9 range or mixture of such aromatics. is equivalent to benzene in practicing ,the process of the invention. The areas ABCD and EFGH of Fig.2 are applicable'likewise when any of these saturate and arc matic' compounds are used in place of pentane and benzene.

The feed to the dewaxing step, in addition to having its solvent composition asv prescribed by Fig. 2, should have a volume ratio of solvent to charge stock compo nentsof at least 1:1. This ratio should be higher for charge stocks of relatively high boiling range but gen-v erally need not exceed 6:1 even for the heaviest stocks. In the process illustrated in Fig. 2, the desired solvent 10 011 ratio is secured by adding to the rafi'inate material in line 31 solvent from line 32'which has been recovered from the products of the dewaxing step. 7

The rafiinate-solvent material of adjusted composition iscooled in chiller 33 tothe required dewaxingtempera ture and 'is then passed through line 34 to the dewaxing zone illustrated diagrammatically at 35. The dewaxing temperatures usually will range from 5 to 25 F. below the desired pour point of the dewaxed oil product, de-' pending upon the particular composition of solvent used. For example, if an oil of 0 F. pour point is desired, the temperature of 'the mixture fed through line 34 generally should be in the range of 5 F. to 25 F. In zone 35 the wax crystals are filtered from the liquid and are washed with additional chilled solvent obtained from line Y32 and chiller 36. The amount of such wash solvent usually' should be 40150% by volume based onthe amount of charge stock'components fed, to zone 35, this amountbeing in addition to the amountof solvent previously specified for the feed to the dewaxing step.

.li'rom'the dewaxing operation the wax product is transferred, 'as "indicated by line 37,"to' distillation tower '38' I for removal of solvent carried by the Wax, and the resulting slack wax is withdrawn from the system through line 39. The oil and solvent mixture from dewaxing zone 35 is sent through line 40 to tower 41 from which the solvent is recovered through line 42. From the base of tower 41 refined oil of high viscosity index and low pour point is Withdrawn by means of line 43.

The solvent recovered from distillation towers 38 and 41 is partly recycled through line 32 for re-use in the dewaxing step as previously described, and the remainder is passed through line 44 back to desorbent tank 17. Thus the exact composition of the desorbing agent used in adsorber 11 will be determined by the combined compositions of the streams returned to tank 17 by means of line 26 and line 44.

A specific example of the process of Fig. 1 employing only ethylene dichloride and pentane as the solvent materials is as follows, based on treating 1000 bbls./day of a waxy charge oil having an A. P. I. gravity of 30, S. U. viscosity of 150 at 100 F., a viscosity index of 70 and an aromatic content of 25% by Weight.

Thecha-rge oil is diluted with 760 bbls./ day of pentane from tank 12 and the mixture is fed alternately to adsorption zone 11, each addition of charge being followed by the introduction of desorbing agent composed of 1200 bbls. of ethylene dichloride and 240 bbls. of pentane. In each cycle of this adsorption-desorption operation the charge oil and ethylene dichloride fed to the adsorber amount, respectively, to 0.10 and 0.12 gal. per lb. of silica gel. The extract fraction obtained from the ad sorber is composed of 820 bbls. of ethylene dichloride, 200 bbls. of pentane and 262 bbls. of aromatic-rich oil,- and the solvent components are distilled therefrom and returned to tank 17. The raffinate fraction, which is composed of 380 bbls. of ethylene dichloride, 800 bbls. of pentane and 738 bbls. of saturate-rich oil including wax, is distilled in tower 22 whereby 760 bbls. of pentane are removed and returned to tank 12. The partially depentanized raflinate fraction is admixed with 1055 bbls. of recycle solvent composed of 960 bbls. of ethylene dichloride and 95 bbls. of pentane, and the mixture is chilled to about F. and dewaxed in zone 35. About 525 bbls. of wash solvent, composed of 476 bbls. of ethylene dichloride and 49 bbls. of pentane, from chiller 36 is used. Upon removal of solvents from the products, there is obtained from tower 41 about 590 bbls./day of dewaxed oil having a pour point of 0 F., an aromatic content of 9% by weight and a viscosity index of 95 and about 148 bbls./day of slack wax from tower 38.

Another specific example of the process of Fig. 1 in which the dewaxing solvent is a mixture of benzene and 80% ethylene dichloride is as follows, again based on treating 1000 bbls./day of the same waxy charge oil.

The charge oil is admixed with 800 bbls. of pentane and the mixture is fed to the cyclic operation of adsorber 11. 1400 bbls. of desorbing agent containing 200 bbls. of pentane with the remainder being ethylene dichloride plus benzene are used in the desorbent step. The extract fraction, which is composed of 260 bbls. of aromaticrich oil, 200 bbls. of pentane and 820 bbls. of ethylene dichloride plus benzene, is distilled in tower to recover the solvent. The raffinate fraction is composed of 738 bbls. of saturate-rich oil, 800 bbls. of pentane, 304 bbls. of ethylene dichloride and 76 bbls. of benzene. This material is distilled in tower 22 and all of the pentane is recovered therefrom for re-use as charge diluent. The resulting depentanized raflinate material is admixed with 1095 bbls. of recycled solvent containing about 876 bbls. of ethylene dichloride and 219 bbls. of benzene and the mixture is cooled to about -10 F. and then fed to dewaxing zone 35. About 515 bbls. of wash solvent is also fed to the dewaxer through chiller 36. Upon distilling oi the solvents from the resulting fractions, products are obtained with essentially the same qualities and in about the same yields as in the preceding example.

A further modification of the process illustrated by Fig. 1 can be made within the scope of the invention for use preferably when ethylene dichloride and the saturate hydrocarbon diluent are the only solvent materials present in the system. In such case it may be desired to distill as much as possible of the pentane from the rafiinate fraction so that maximum dilution of the charge stock can be achieved without providing an additional distillation tower for removing pentane from the recovered desorbing agent. The present modification provides for the removal of all the pentane in the raffinate fraction which is introduced to tower 22. The resulting depentani'zed material is then admixed with a portion of the distillate from tower 25 which is supplied by means of dashed line 46. This distillate, while being composed mainly of ethylene dichloride, contains pentane in a proportion higher than its minimum permissible proportion in the dewaxing solvent. Typically, this distillate will contain 15-20% pentane whereas the pentane content of the dewaxing solvent needs to be only 2% as a minimum and preferably only at least 5%; hence the necessary pentane can readily be supplied to the depentanized rafiinate fraction by solvent recovered from tower 25. This same procedure maybe used, if desired, when the dewaxing solvent contains both benzene and pentane in admixture with the ethylene dichloride, although in such case there generally is no advantage in operating in this manner as compared to the procedure heretofore described for Fig. 2.

Other modifications of the process are permissible within the purview of the invention. For example, the adsorption-desorption operation need not be conducted with a fixed bed of silica gel as above described and can be practiced by circulating the adsorbent particles through countercurrent contacting zones wherein the adsorption and desorption steps are carried out continuously. Other variations in the process will be apparent in the light of the foregoing disclosure.

We claim:

1. Method of preparing a lubricating oil having a low pour point and improved V. I. from a waxy lubricating oil stock which comprises diluting the stock with a saturate hydrocarbon diluent of the C3-C6 range, treating the diluted stock with silica gel to selectively adsorb aromatic constituents, displacing hydrocarbons from the silica gel by means of a liquid desorbing agent containing ethylene dichloride and obtained as hereinafter specified, obtaining from the silica gel treatment (1) a first ratiinate fraction containing saturate components of said stock including wax in admixture with desorbing agent and saturate hydrocarbon diluent, and (2) an extract fraction containing aromatic components of said stock in admixture mainly with desorbing agent, distilling the first rafiinate fraction to remove overhead a major portion of the diluent contained therein while recovering as bottoms a second ralfinate fraction comprising saturate components of the charge together with substantially all the desorbing agent present in the first rafiinate fraction, adding additional desorbing agent to the second raffinate fraction, regulating the distillation and the addition of desorbing agent so as to produce an admixture of a dewaxing solvent and charge saturates in which the ratio of the total solvent to charge stock components therein is within the range by volume of 1:1 to 6:1 and the total solvent composition conforms to the area ABCD of Fig. 2, cooling the admixture to a Wax crystallizing temperature, separating wax from the cooled mixture, recovering solvent from the dewaxed oil and Wax products, recovering desorbing agent from said extract fraction, and utilizing such recovered solvent in admixture with recovered desorbing agent as the said liquid desorbing agent.

2. Method according to claim 1 wherein said total solvent composition conforms to the area EFGH of Fig. 2.

3. Method according to claim 1' wherein the dewaxing solvent. is composed of 70-98% of ethylene dichloride and 230% of saturate hydrocarbon of the C3-C6 range.

4. Method according to claim 3 wherein said saturate hydrocarbon is pentane.

5. Method according to claim 1 wherein the dewaxing solvent is composed of 40-98% of ethylene dichloride and 2-60% of aromatic hydrocarbon of the C6-C9 range.

6. Method according to claim 5 wherein said aromatic hydrocarbon is benzene.

V 7. Method of preparing a lubricating oil having a low pour point and improved V. I. from a waxy lubricating oil stock which comprises diluting the stock with a staurate hydrocarbon diluent of the C3-C6 range, treating the diluted stock with silica gel to selectively adsorb aromatic constituents, displacing hydrocarbons from the silica gel by means of a desorbing agent composed of ethylene dichloride, an aromatic hydrocarbon solvent of the C6-C9 range and saturate hydrocarbon diluent of the C3-C6 range and obtained as hereinafter specified, obtaining from the silica gel treatment (1) a first raflinate fraction containing saturate components of said stock including wax in solution with ethylene dichloride, aromatic hydrocarbon solvent and saturate hydrocarbon diluent and (2) an extract fraction containing aromatic components of said stock in solution With such solvent components, distilling the first rafiinate fraction to remove overhead a major portion of the saturate hydrocarbon diluent contained therein While recovering as bottoms a second raffin'ate fraction comprising saturate components of the charge together with substantially all the ethylene dichloride and aromatic hydrocarbon solvent present in the first rafiinate fraction, adding additional ethylene dichloride and aromatic hydrocarbon solvent to the second rafiinate fraction, regulating the distillation and the addition so as to produce an admixture of amixed dewaxing solvent and charge saturates in which the ratio of the total solvent to charge stock components therein is within the range by volume of 1:1 to 6: 1 and the total solvent composition is within the area ABCD of Fig. 2, cooling the admixture to a wax crystallizing temperature, separating wax from the cooled mixture, recovering solvent from the dewaxed oil and wax products, recovering solvent from said extract fraction, and utilizing a mixture of such recovered solvents as the said liquid desorbing agent.

8. Method according to claim 7 wherein the saturate hydrocarbon diluent is pentane and the aromatic hydrocarbon solvent is benzene.

9. Method according to claim 7 wherein said total solvent composition is within the area EFGH of Fig. 2.

10. Method of preparing a lubricating oil having a low pour point and improved V. I. from a waxy lubricating oil stock which comprises diluting the stock with a saturate hydrocarbon diluent of the C3-C6 range, treating the diluted stock with silica gel to selectively adsorb aromatic constituents, displacing hydrocarbons from the silica gel by means of a desorbing agent composed of ethylene dichloride, an aromatic hydrocarbon solvent of the C6-C9 range and saturate hydrocarbon diluent of the C3-C6 range and obtained as hereinafter specified, obtaining from the silica gel treatment 8 (1) a rafiinate fraction containing saturate components of said stock including wax in solution with ethylene dichloride, aromatic hydrocarbon solvent and saturate hydrocarbon dilent and (2) an extract fraction containing aromatic components of said stock in solution with such solvent components, removing substantially all of the saturate hydrocarbon diluent from said raifinate fraction, adding additional ethylene dichloride and aromatic hydrocarbon solvent to produce an admixture of a mixed dewaxing solvent and charge saturates in which the ratio of the total solvent to charge stock components therein is within the range by volume of 1:1 to 6:1 and the ratio of ethylene dichloride to aromatic hydrocarbon solvent is within the range by volume of 40:60 to 98:2, cooling the admixture to a wax crystallizing temperature, separating wax from the cooled mixture, recovering solvent from the dewaxed oil and wax products, recovering solvent from said extract fraction, and utilizing a mixture of such recovered solvents as the said liquid desorbingagent.

11. Method according to claim 10 wherein the saturate hydrocarbon diluent is pentane and the aromatic hydrocarbon solvent is benzene, and wherein said ratio of ethylene dichloride to aromatic hydrocarbon solvent is Within the range of :30 to :10.

12. Method of preparing a lubricating oil having a low pour point and improved V. I. from a waxy lubricating oil stock which comprises diluting the stock with'a saturate hydrocarbon diluent of the C3-C6 range, treating the diluted stock with silica gel to selectively absorb aromatic constituents, displacing hydrocarbons from the'silica gel by means of a liquid desorbing agent containing a major amount of ethylene dichloride and a minor amount of such C3-C6 saturate hydrocarbon, obtaining from the silica gel treatment (1) a raflinate' fraction containing saturate components of said stock including wax in admixture with ethylene dichloride and saturate hydrocarbon diluent and (2) an extract fraction containing aromatic components of said stock in solution with ethylene dichloride and saturate hydrocarbon diluent, distilling the raffinate fraction to remove substantially all of the saturate hydrocarbon diluent, distilling the extract fraction to remove the solvent therefrom, adding additional desorbing agent to produce an admixture of a mixed dewaxing solvent and charge saturates in which the ratio of the total solvent to charge stock components therein is within the range by volume of 1:1 to 6:1 and the ratio of ethylene dichloride to saturate hydrocarbon diluent is within the range by volume of 70:30 to 98:2, cooling the admixture of regulated composition to a wax crystallizing temperature, separating wax from the cooled mixture, recovering solvent from the. dewaxed oil and wax products, utilizing a portion of the recovered solvent in said regulation, and utilizing the remainder in admixture with the remainder of solvent recovered from said extract fraction distillation as the said liquid desorbing agent.

References Cited in the file of this patent UNITED STATES PATENTS 2,026,336 Wilson Dec. 31, 1935 2,049,059 Goss et al July 28, 1936 2,441,572 Hirschler et a1. May 18, 1948 2,660,552 Blanding Nov. 24, 1953 

1. METHOD OF PREPARING A LUBRICATING OIL HAVING A LOW POUR POINT AND IMPROVED V. I. FROM A WAXY LUBRICATING OIL STOCK WHICH COMPRISES DILUTING THE STOCK WITH A SATURATE HYDROCARBON DILUENT OF THE C3-C6 RANGE, TREATING THE DILUTED STOCK WITH SILICA GEL TO SELECTIVELY ADSORB AROMATIC CONSTITUENTS, DISPLACING HYDROCARBONS FROM THE SILICA GEL BY MEANS OF A LIQUID DESORBING AGENT CONTAINING ETHYLENE DICHLORIDE AND OBTAINED AS HEREINAFTER SPECIFIED, OBTAINING FROM THE SILICA GEL TREATMENT (1) A FIRST RAFFINATE FRACTION CONTAINING SATURATE COMPONENTS OF SAID STOCK INCLUDING WAX IN ADMIXTURE WITH DESORBING AGENT AND SATURATE HYDROCARBON DILUENT, AND (2) AN EXTRACT FRACTION CONTAINING AROMATIC COMPONENTS OF SAID STOCK IN ADMIXTURE MAINLY WITH DESORBING AGENT, DISTILLING THE FIRST RAFFINATE FRACTION TO REMOVE OVERHEAD A MAJOR PORTION OF THE DILUENT CONTAINED THEREIN WHILE RECOVERING AS BOTTOMS A SECOND RAFFINATE FRACTION COMPRISING SATURATE COMPONENTS OF THE CHARGE TOGEHTER WITH SUBSTANTIALLY ALL THE DESORBING AGENT PRESENT IN THE FIRST RAFFINATE FRACTION, ADDING ADDITIONAL DESORBING AGENT TO THE SECOND RAFFINATE FRACTION, REGULATING THE DISTILLATION AND THE ADDITION OF DESORBING AGENT SO AS TO PRODUCE AN ADMIXTURE OF A DEWAXING SOLVENT TO CHARGE STOCK COMPONENTS THEREIN OF THE TOTAL SOLVENT TO CHARGE STOCK COMPONENTS THEREIN IS WITHINTHE RANGE BY VOLUME OF 1:1 TO 6:1 AND THE TOTAL SOLVENT COMPOSITION CONFORMS TO THE AREA ABCD OF FIG. 2, COOLING THE ADMIXTURE TO A WAX CRYSTALLIZING TEMPERATURE, SEPARATING WAX FROM THE COOLED MIXTURE, RECOVERING SOLVENT FROM THE DEWAXED OIL AND WAX PRODUCTS, RECOVERING DESORBING AGENT FROM SAID EXTRACT FRACTION, AND UTILIZING SUCH RECOVERED SOLVENT IN ADMIXTURE WITH RECOVERED DESORBING AGENT AS THE SAID LIQUID DESORBING AGENT. 